Boron alloy



Patented Aug. 16, 1938 umrao STATES PATENT OFFICE I BOBON ALLOY AnthonyG. de Golyer, New York, N. Y.

No Drawing.

The present invention relates to a new and useful alloy and relatesparticularly to an alloy containing boron, zirconium, tungsten, chromiumand cobalt, which is characterized by being responsive tothermal'treatment for the improvement of physical properties.This'applicatio'n is a continuation in part of my co-pending applicationSerial No. 721,771, filed April 21, 1934.

An object of the present invention is to provide an alloy especiallyadapted for use as metal cutting or forming tools, the cuttingefliciency of which is several times greater than that of present knownhigh speed steels and other alloys. A further object of this inventionis to provide an alloy which is free from, or substantially free fromcarbon and which is readily amenable to thermal treatment, by means ofwhich the hardness, tensile strength, cutting emciency and otherphysical properties and characteristics may be accurately controlledover a comparatively wide range.

I have found through experiment that by alloying or otherwise intimatelycombining boron, zirconium, tungsten, chromium and cobalt within therange of boron 0.50% to 5%, zirconium 2.00% to 20%, tungsten 1% to lessthan 10%, chromium 1% to 25% and cobalt substantially the balance, thatI obtain metallic compositions which in combination possess materiallyimproved physical properties compared to those of heretofore knownalloys or compositions intended for the cutting or working of metals.

Alloys of this invention may be used in the cast condition butapproximate maximum values of hardness and certain other importantphysical properties can be developed only through thermal treatment, orthrough mechanical working and subsequent thermal treatment. Bodies ofthe alloys which have been subjected to such treatment are particularlyvaluable for use as tools, dies and the like for the cutting ormechanical-working of metals.

My alloy may be used in the as-cast condition, or it may be forged androlled or otherwise mechanically worked. I have found that both the castand forged material are amenable to thermal treatment. of this alloy mayhave a hardness of from 50 to on the Rockwell C scale and by subjectingthe material to suitable thermal treatment, such as quenching from atemperature higher than 1,000 0., the hardness maybe lowered to anapproximate range of from 40 to 47 Rockwell C. In this condition thebodies may be ground, shaped or formed, if desired. The alloy may sub-For example, cast or forged bodies' Application June 13, 1936, SerialNo. 84,999%

sequently be submitted to a second thermal treatment, such as heating toa temperature of less than 1,000" C. for a period of from one or morehours, by which the hardness may be increased to from approximately 60to,70 Rockwell C. In the latter condition the alloy is especiallyvaluable for the cutting or mechanical working of a large number ofmetals and alloys, as well as numerous non-metallic materials. Animportant property of the alloy is that virtually all of the maximumhardness, developed by thermal treatment, is retained when the alloy issubjected to elevated temperatures, e. g. such as are generated in thetip of a tool cutting metal at high speed. Although the alloy has a highdegree of hardness, especially after thermal treatment, it is remarkablyresistant to failure from sudden or repeatedshock.

The more important distinctive and valuable advantages are, apparently,due to the presence of appreciable amounts of boron in the composition,in conjunction with the other essential component elements within thepercentages specified herein.

Although I usually prefer to have the alloy which is to be used as ametal cutting tool, for example, composed principally of boron;zirconium, tungsten, chromium and cobalt, I' have found that in manyinstances the tungsten may be supplanted in whole or in part bymolybdenum, or .uranium, or both. The results of my investigationsindicate that alloys composed principally of boron 0.50% to 5%,zirconium 2% to 20%, metal from the group tungsten, molybdenum anduranium 1% to less than 10%, chromium 1% to.

25%, and the balance substantially cobalt, possess substantially thesame valuable physical properties and characteristics as the abovedescribed composition containing only tungsten in combination withboron, zirconium, chromium and cobalt. Therefore, the alloy of thepresent invention comprises boron 0.50% to 5%, zirconium 2% to 20%,metal selected from the group tungsten,

11%, and cot substantially the balance.

An objective of the present invention is to pro tended for metal cuttingtools. Although 1 preier to have the alloys of this invention entirelyfree from carbon, in many instances I have found carbon present in thenature of an impurity incidental to manufacture. It is important torestrict the amount of carbon so present to a maximum of about 0.15%, asI have found that the presence of higher percentages of this element notonly tend to embrittle the alloy, but also to retard or inhibit thedesired and necessary reactions during thermal treatment. Furthermore,the presence of appreciable amounts of carbon decreases the red hardnessof the alloy, 1. e. hardness at temperatures of approximately 550 C. andhigher.

By reason of the fact that the elements forming the essential componentsof the alloy of the present invention invariably are contaminated withother elements when produced in commercial quantities, the alloys of myinvention usually contain insignificant amounts of one or more elementsin the nature of impurities incidental to manufacture. The amount ofsuch impurities should be restricted to percentages which are noteffective on the physical properties or characteristics of the alloy. Ihave found that the amount of any one of such incidental impuritiesshould be restricted to percentages not exeeding 1%, and

' in many instanes to materially lower percentages. The presence oflarger amounts of such impurities not only lowers the tensile strengthand impact value of the present alloy, but greatly retards, or entirelyinhibits. the desired physical reactions during thermal treatment.

My investigations indicate that the preferred structure of a body of thepresent alloy, particularly after thermal treatment, comprises at leasttwo principal constituents: one, a relatively amazes zirconi 5.25%,molybdenum chromium hard intermetallic compound of boron with one ormore of theother essential components; and,

second, a solid solution of two or more of the essential componentswhich has a. lower degree of hardness andfunctions as a matrix. In someinstances the structure will contain a third constituent in the natureof an eutectoid. The ratio of the constituents in any particular body ofthe alloy may be accurately controlled' and fixed over a wide range bymeans of thermal treatment, or mechanical working and subsequent thermaltreatment.

By reason of the combined advantageous physical properties possessed bythe alloy of the present invention, tools and other articles composed ofthis alloy may be operated efllciently and economically under conditionswhich are impossible or uneconomical with tools or articles composed ofheretofore known alloys ormetallic compositions.

By the term "the balance substantially all cobalt, or the balancecobalt, in the foregoing and in the following claims, I intend that thealloy of the present invention comprises boron, zirconium, metal of thegroup tungsten, molybdenum and uranium, and chromium within thepercentage limits specified, with the remainder cobalt except forineffective amounts of impurities which may be present incidental tomanufacture.

I claim:

1. A precipitation hardened alloy consisting of boron 0.50% to 5%,zirconium 2% to 20%, metal from the group tungsten, molybdenum anduranium 1% to less than chromium 1% to 25%, the balance cobalt.

2. A precipitation hardened alloy consisting of boron 0.50% to 5%,zirconium 2% to tungsten 1% to less than 10%, chromium 1% to the balancecobalt.

3. A-precipitation hardened alloy consisting of boron 0.50% to 5%,zirconium 2% to 20%, molybdenum 1% to less than 10%, chromium 1% to 25%,the balance cobalt.

ANTHONY G. M: GOLYER.

